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2 Sheets-Sheet '1. F. J. SPRAGUE.

ELECTRICAL INDICATOR.

- .NO. 314,891 Patented Mar. 31, 1885.

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P; J. SPBAGUE.

v ELECTRICAL INDICATOR. No. 314,891. Patented Mar. 31, 1885.

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York, have invented a new and useful Im- UNITED STATES I PATENT OFFICE.

FRANK J. SPRAGUE, OF NEW YORK, N. Y.

ELECTRICAL INDICATOR.

SPECIFICATION forming part of Letters Patent No. 314,891, dated March31, 1885.

Application filed January 24, 1884.

To aZZ whom it may concern:

Be it known that I, FRANK J. SPRAGUE, of New York, in the county andState of New proveinent in Electric-Current Indicators, of which thefollowing is a specification.

The object of this invention is to produce an indicator of variations inelectric current which shall operate entirely by such variations, andshall not be influenced in any way, or at least to any practical extent,by permanent magnetism. Such indicators, as they have heretofore beenmade, have employed permanent magnetism in one way or another, either bythe use of steel horseshoe-magnets or polarized steel needles; but wherepermanent magnets are used the instruments are affected by theproximity-of dynamo-electric machines and by terrestrial magnetism.

In my invention I affect the indicating devices entirely by electricity,and I accomplish this by the use of a core partly or wholly inclosed bya conductor which may be part of the circuit the variations of whosecurrent are to be indicated, or part of a circuit which receives currentfrom a separate source, such core being provided with a magnetic movableextension which is in such contiguity to a conductor of the circuit thevariations of whose current are to be indicated as to 'be affected whenmagnetized by variations in the magnetic field surrounding theconductor, due to the current in said conductor, its movements beingsuitably indicated. The core may be pivoted within the coil and themovable extension attached thereto, so that the whole will movetogether, and this is perhaps the simplest construction. In this twoextensions are preferably employed, one at each end of the core, to givea greater movement; or the core may be stationary and the extensionmovable independent-1y thereof. An opposing force to the movementscaused by the current variations is provided, such force being variable,so that the indicator may be adjusted for the different currentsemployed in the different situations where it is to be used, the movableextension being adjusted to acertain position for no current, anddeflected therefrom to a greater or less extent, according to i (Nomodel.)

the current which passes. This main idea of my invention is susceptibleof very many modifications, some of which will be hereinafter set forth.

In the construction of my apparatus which V I especially prefer toemploy, asmall portion of the conductor is formed into a coil, and thesoft-iron core is placed centrally within said coil and pivoted at itsends. Upon each projecting end of the core is placed an arm at rightangles to said core, said arms extending in opposite directions andparallel to the conductor. One of these arms carries a needle orpointer, the end of which travels upon a scale. An adjustable weight orspring is attached to the core, opposing the movement of theindicating-arm. I may employ for this purpose a weight sliding upon anarm suspended from the core. The arms attached to the core aremagnetized from said core when current passes in the coil, and thereforetend to place themselves at right angles to the conductor in proximityto which they are. The weight is so adjusted that with no currentpassing the needle will stand at a certain selected point upon thescale. Then as the current increases the arm will move more toward aright angle with the conductor in a direction dependent on the directionof the current, and as it diminishes in the opposite direction. Theextent of these movements is indicated by the needle upon the scale. Thescale is preferably graduated in amperes, so that the current flowing atany time is indicated.

My invention is illustrated in the annexed drawings, in which Figure 1is a front elevation of the preferred apparatus, and Fig. 2 a sideelevation and partial section thereof.

The remaining figures are diagrams il1ustrating various modifications.

- Referring first to Figs. 1 and 2, A is a conductor of the circuit thevariations of whose current are to be indicated. The conductor is'brokenand connected to the indicating apparatus, as shown, and held byset-screws a a. Within the apparatus the current passes through thestandard 13, the coil 0, and the are D. The last supports the scale E.The soft-iron core F is placed centrally within the coilCand pivoted atc 0, the screws d d, which support it, being held, one by the standardB, the other by the arm 6, extending from the lower portion of thearc-piece D. The screws d d are insulated from the parts through whichthey pass. Upon the core F, outside the coil 0, are placed the arms Gand G. Arm G carries a needle, H, the end of which travels across thescale E. From the core extends also the arm I, carrying an adjustableweight, which is the milled nut K. This weight furnishes the opposingforce for the current, and is adjustable, so that such force may be madeto correspond with the currents of greater or less power,which occur inthe different situations in which the indicator may be used, the weightbeing adjusted 'to the proper point for the circuit in question. Whencurrent passes in the coil 0, the core F becomes magnetized, and alsothe arms G G, which form extensions of the core. These magnetized armsare then affected by the current in the conductor formed by the standardB and are D, tending to place themselves at right angles to theconductor, and variations in the current cause an increase or diminutionof such tendency. The core turns on its pivots opposed by the weight K.The movements are indicated by the needle upon the scale. It is, ofcourse, not essential to use two arms, one at each end of the core; butit is evident that an increased effect will be produced by thisconstruction.

I will describe in detail the various modifications illustrated by theremaining figures. In Fig. 3 the two arms G G extend in the samedirection from the core F, and the conductor beyond the coil 0 isextended so that both arms are in proximity to it. The same effect isproduced as already described.

In Fig. 4 the magnetization is produced by a shunt, f f, while thedeflection is caused by the main conductor directly. The shunt may havesuch resistance as to permit any desired proportion of the current topass in the coil.

In Fig. 5 the core is magnetized by a separate circuit, 9 g, from abattery or other source of electricity. This furnishes a constantmagnetization, while when the coil is in the line or shunt themagnetization of the core and needle-arm is increased and decreased bythe current variations, so that such variations produce a double effectupon the needle. In such a case the original graduation of the scale isof course made to conform with this effect.

In Fig. 6 one conductor, A, of the circuit is wound around the core, andthe extensions of the core are in proximity to both the conductors A A,so that it is acted upon by both.

In Fig. 7 two conductors are wound into the coil and in oppositedirections, so that a double magnetizing effect or a differential effeetis produced, according to the direction of the current.

Fig. 8 also illustrates a form giving either a differential or acumulative action, the two conductors being wound in the same direction.

Fig. 9 shows a stationary core, with the movable needle-arm G detachedfrom it, and

magnetized from it by induction. In Fig. 10 also the core is stationary,the needle-arm G being pivoted upon it.

In Fig. 11 the detached arm G extendslongitudinally, instead of at rightangles, from the core, tending to move to a right angle with theconductor, as before.

Figs. 12, 13, 14, and 15 show other ways of producing the opposingforce. In Fig. 12 an adjustable spring, L, is attached to an armextending from the core.

In Fig. 13 the weight K is suspended by a cord, M, passing over apulley, N. In this case the weight is constant, instead of varying withthe movement of the core, as would be the case in thepreviously-described forms.

In Fig. 14 the adjustable weight is suspended from a pulley eccentric tothe core, and is adjusted by adjusting the eccentric on its shaft, or byadding weights.

In Fig. 15 two equal adjustable eccentrics are employed, each supportinga weight.

It is evident that each of the different mechanical arrangements shownmay be employed in connection with any of the various circuitarrangements.

WVhile I have described and prefer to use a core whose magnetism is dueentirely to the current passing around it, yet it is evident that a corepermanently magnetized to a certain extent and intensified by thecurrent might be used without departing from the spirit of my invention;and I consider this practically the equivalent of the preferredconstruction. 7

IVhat I claim is 1. In an electrical indicator the combination of a coilforming part of a circuit, a core magnetized from said coil, and amovable arm or needle magnetized from-said core and placed in proximityto a conductor of the circuit the variations of whose current are to beindicated, substantially as set forth.

2. In an electrical indicator, the combination of a coil forming part ofa circuit, a movable core magnetized from said coil, and a magneticextension attached to said core and placed in proximity to a conductorof the circuit, substantially as set forth.

3. In an electrical indicator, the combination of a coil forming part ofa circuit, amovable core magnetized thereby, and two magnetic extensionsof said core, both affected by the current in the conductor,substantially as set forth.

4. The combination, with the coil, the movable core magnetized thereby,and the one or more extensions in proximity to the conductor, of an adjustable weight or spring attached to said core and opposing the movementof said extension or extensions, substantially as setforth.

5. The combination, with the coil, of the core pivoted at its endscentrally within said coil, the one or more magnetic extensions of IIOsaid core situated in such proximity to a con- This specification signedand witnessed this ductor of the circuit the variations of whose 22d dayof January, 1884.

current are to be indicated as to be affected by variations in themagnetic field surround- FRANK SPRAGUE' 5 ing such conductor, and thescale indicating Witnesses:

the movements of said extensions, substan- H. W. SEELY,

tialiy as set forth. 0. F. HARRINGTON.

